An electrochemical impedimetric immunosensor was developed for the detection of the neuropeptide Corticotropin Releasing Hormone (CRH) based on the immobilization of half-antibody fragments on gold nanoparticles (AuNp). Then, the optimal conditions for the obtainment of AuNp through electroplating on a bare gold electrode were studied. The results showed that the obtainment of AuNp at a fixed potential of -0.2 V for 330 s, at 80 degrees C and 2.10-3 mol.L-1 of HAuCl4 generates an adequate nanostructured surface and is a highly reproducible method. Also, the optimal conditions for immobilizing the half-antibody on AuNp were studied. The interaction of the CRH with the recognition layer of the immobilized half-antibody on the nanostructured surface was carried out by incubation at 4 degrees C for 2 h. A dissolution of [Fe(CN)(6)](4)/[Fe(CN)(6)](3-) as a redox probe was used to study the electrochemical responses of the nanostructured surface and the immobilization processes of the half -antibody and detection of CRH, using cyclic voltammetry and electrochemical impedance spectroscopy. An immunosensor was obtained for the specific detection of CRH, within a range of 10.0-80.0 mu g mL(-1), with a limit of detection of 2.7 mu g mL(-1) and a limit of quantification of 9.2 mu g mL(-1) . Additionally, the association constant between the CRH and the immobilized half -antibody was calculated at 1.96.10(5) M-1.Regular 2015FONDECYTFONDECYT